1. Field of the Invention
This invention relates to a liquid detergent composition, and, more particularly, to a liquid detergent composition having low irritation to the skin, exhibiting an excellent antibacterial effect, and particularly giving superior anti-dandruff and deodorant effects when used as a detergent for washing the scalp and hair.
2. Description of the Background Art
Conventionally, synthetic anionic surfactants such as alkyl sulfates, ethoxylated alkyl sulfates have widely been used in liquid detergent compositions for skin and hair. They are excellent in detergency and foaming capability, however, they have a drawback of strong irritation to the skin and hair. The irritation of these surfactants closely relates to a skin-barrier function and to cell division of keratinocytes. There has been a report [Gibson W. T. et al., Food Chem. Toxic., 23, 103, (1985)] that a skin-barrier function is lowered and cell division of keratinocytes- is promoted with increased irritation of surfactants.
In the meantime, it is believed that dandruff is mostly caused by abnormal desquamation of horny cells and sebaceous hypersecretion and worsened by the growth of bacteria. For anti-dandruff shampoo compositions, therefore, synthetic anionic-surfactants and an antibacterial agent are usually incorporated to wash the secretive sebum and restrain the growth of bacteria. However, dandruff is often developed in a relatively short time after shampooing, although they frequently shampoo the hair and scalp with these anti-dandruff shampoo compositions. This is because the more frequent shampooing increases the chances of contacting surfactants having high irritation to the skin with the scalp, thus irritating the skin and lowering a barrier function of the skin, and promoting cell division of keratinocytes resulting in the acceleration of the development of dandruff.
As for body detergent compositions, most of these detergent compositions usually contain highly irritant surfactants. These surfactants inevitably give an adverse effect on a skin-barrier function. In this respect, washing the skin with these detergents consequently weaken the resistance of the skin against external stimuli such as microbial contagion to the skin.
From the above facts, the development of detergent compositions which can restrain dandruff and never weaken the resistance of the skin against external stimuli has been desired.
In view of this situation, the present inventors have undertaken extensive studies to resolve the above-mentioned problem. As a result, the inventors have found that by incorporating a saccharide nonionic surfactant and an antibacterial agent into a detergent composition, the above-mentioned problem could be solved and also an antibacterial effect of the detergent composition was greatly improved. This finding has led to the completion of this invention.